Is refraining from attending social occasions out of grief for the death of one's mother considered forbidden?

Mourning for the deceased is not permissible for more than three nights, except for a wife mourning her husband, for whom it is four months and ten days. Mere sadness and weeping, without wailing, is natural and one is not held accountable for it. However, grief should not prevent one from accepting an invitation to a feast (walima), which must be answered, or other recommended invitations, because that is a right of a Muslim upon his brother. Furthermore, mingling with people and attending their gatherings helps in finding solace.